Optical fibers and devices such as optical amplifiers, optical demultiplexers, optical multiplexers, and optical switches that are used to perform communications using optical communication paths have peculiar optical propagation characteristics, and influence the quality of optical signals transmitted. As technology for automatically compensating such propagation characteristics, a method of feedback-controlling dispersion compensators based on signal monitoring results in a receiving end is disclosed in patent document 1: Japanese Patent Laid-Open No. 2005-64905 and patent document 2: Japanese Patent Laid-Open No. 2002-208892.